1. Field of Technology
The present invention relates to an image scanner and to an image scanning method for reading images from media such as paper and cards.
2. Description of Related Art
Image scanners are commonly used to acquire image data from paper, cards, and other types of media (referred to below as the “scanned medium” or “original”). Image scanners image the scanned medium by emitting light to the scanned medium from LEDs or other light sources in a scan head with the scan head effectively in contact with the scanned medium, and then detecting the light reflected from the scanned medium with image sensors also disposed to the scan head.
Image scanners are available in two general types: flatbed and sheetfed. With flatbed scanners the original is placed on a document glass and the scan head moves across the document surface to image the original. With sheetfed image scanners, however, the scan head remains stationary while the original is conveyed past the scan head while being pressed to the scan head to image the original.
Flatbed scanners tend to be large because there must be sufficient space inside the scanner to house the mechanism for moving the scan head. Sheetfed scanners can therefore be easily made smaller than flatbed scanners.
FIG. 13 is a schematic diagram of a conventional sheetfed image scanner 200. With this scanner 200, original sheets P placed on a supply tray 202 are raised by a raising/lowering tray 203, picked up by the supply roller 204, and conveyed from the insertion slot F into the scanner 200. The sheet P is then transported by the separation roller pair 205 and feed roller pair 206 to the image sensor 201, and the original is imaged by the image sensor 201. The imaged sheet P is then discharged by exit roller pair 207 from the exit opening R to the exit tray 208. A scanner like the scanner 200 is known from JP-11-284801-A.
As will be apparent from FIG. 13, the insertion slot F, image sensor 201, and exit opening R are arranged in this order along a straight transportation path, and the scanned medium (original sheet P) is conveyed in one direction in this conventional scanner 200. A problem with this scanner 200, therefore, is that if the scanner is placed with the insertion slot F at the front, the scanned medium is discharged from the back of the scanner 200. This makes it difficult to remove the scanned media, and operation is inconvenient.
Furthermore, if the original is inserted skewed to the transportation path of the image scanner, it is either conveyed diagonally through the transportation path or the direction of travel is corrected by a guide member in the transportation path, and the original is therefore either imaged at an angle or the captured image is turned partway through. If the original is an identification card containing a photograph of the individual's face, this can result in a distorted image of the individual's face or even render the captured image unusable as data for individual identification.
In addition, if the scanned medium is inserted at an angle to the image scanner, the medium could become stuck inside the transportation path, resulting in a paper jam.
Multiple detectors (such as a paper insertion detector, a leading edge detector, trailing edge detector, and discharge detector) are also needed if skewed insertion of the original to the image scanner is to be detected and corrected before the user sees the captured image and only then realizes the skew. This increases the cost and inhibits reducing the size of the image scanner, and creates increased complexity in that the output signals from the multiple detectors must be processed.